| H band | where only thick myosin filaments are found |
| I band | where only thin actin filaments are found |
| A band | where both actin and myosin are found
actin and myosin overlap |
| M line | attachment for myosin filaments |
| Z line | attachment for actin filaments |
| properties of fast twitch fibres | contract quickly
fewer capillaries
fewer mitochondria
large store of calcium ions in the sarcoplasmic reticulum
large amounts of glycogen
fatigues faster due to greater lactate formation
white - little myoglobin |
| slow twitch fibres | contract slowly
large network of capillaries
lots of mitochondria
small store of calcium ions in the sarcoplasmic reticulum
fatigues slower due to less lactate formation
red - lots of myoglobin |
| define negative feedback | the product of a process that counteracts change to maintain an equilibrium around a normal level |
| define positive feedback | a process that causes an increase in change away from the normal level |
| homeostasis | maintenance of a constant internal environment
changes are detected by receptors
controlled by negative feedback
controls temp, salt, water and CO2 |
| how does homeostasis maintain dynamic equilibrium during exercise? | changes cardiac output
changes breathing rate
balances temp |
| why is homeostasis important in mammals? | metabolic reactions are controlled by enzymes
enzymes work best at a narrow range of pH and temp
so it is important to maintain a steady environment |
| what is dynamic equilibrium? | when the rate of the forward reaction is equal to the reverse reaction
it is dynamic because the molecules react continuously
it is in equilibrium because there is no overall net change |
| role of the hypothalamus in homeostasis | has thermoreceptors which detect changes in blood temp
stimulates effectors to decrease or increase the body temp |
| mechanisms of thermoregulation during exercise | vasodilation of skin capillaries
sweating
hairs lay flat |
| what are the two methods of medical technology that allows those with injuries/disabilities to do sport? | keyhole surgery
prosthesis |
| keyhole surgery | non invasive
uses fibre optics
repairs damaged joints quickly
recovery time is shorter
cheaper than conventional methods |
| prosthesis | artificial body part
allows people to regain the appearance/function of a particular body part
can be connected internally or externally |
| the effects of moderate exercise on the immune system | increases the number and activity of natural killer cells found in the blood and lymph
increases blood HDL and reduces LDL
helps maintain a healthy weight
reduces the risk of CHD, diabetes and some cancers
improves mental wellbeing |
| the effects of vigorous exercise on the immune system | reduces number and activity of: natural killer cells, phagocytes, B cells, T helper cells, cytokines and antibodies |
| the effects of little exercise on the immune system | leads to obesity
increased risk of CVD and diabetes
immune system suppressed
increased levels of LDL's |
| the effects of vigorous exercise on the joints/skeletal muscles | damage to muscle fibres
articular cartilage can wear away
the kneecap may stop gliding across the femur
bursae can swell up with extra fluid
damage to ligaments |
| why would athletes take testosterone? | increases protein synthesis in muscle cells to increase the size and strength of the muscle
testosterone is easily broken down so the chemically modified anabolic steroid nandrolone was made to overcome the problem
urine tests to find the ratio of testosterone to epitestosterone |
| why would athletes take blood transfusions? | increases the number of blood cells so more oxygen can be transported to the blood
athletes can use their own blood or someone else's with the same blood type
increased risk of blood clot, heart attack, stroke |
| why would athletes take EPO's? | a peptide hormone naturally produced by the kidneys
stimulates the formation of new red blood cells in the bone marrow
increased risk of thrombosis when EPO levels are too high
it is hard detecting EPO doping because EPO naturally occurs in the body however scientist have found a way to distinguish between synthetic and natural EPO |
| why would athletes take HGH? | human growth hormone
increases lean body mass and decreases fat mass
blood test to distinguish between the natural and synthetic HGH |
| why would athletes take creatine? | amino acid derived
naturally found in meat and fish
carried in the blood to tissues
helps build lean muscle mass and reduce recovery time
creatine is not banned from athletes use |
| examples of peptide hormones | EPO, insulin, human growth hormone |
| examples of steroid hormones | testosterone, estrogen, progesterone |
| what is a hormone? | a chemical substance produced by the endocrine gland transported in the blood
they alter the activity of tissues |
| how do peptide hormones reach their target cell? | binds to receptors on the cell surface membrane
this activates a second messenger
the second messenger will activate the enzymes or transcription factors that will alter the function of the cell |
| how do steroid hormones reach their target cells? | the hormone pass through the membrane via simple diffusion
it binds to the receptors in the cell
the hormone-receptor complex acts as a transcription factor switching enzyme synthesis on or off |
| what are transcription factors? | proteins
binds to specific base sequences of DNA
stimulates or prevents the transcription of a gene |
| why can steroid hormones go across the membrane but peptide hormones can't? | steroid hormones are made of lipids so they can enter via simple diffusion
peptide hormones are charged |
| what is the promoter region? | enable the binding of RNA polymerase promoting transcription |
| what is the enhancer sequence? | regulates DNA activity by changing chromatin structure
makes it more or less open to RNA polymerase
open means active gene expression
closed means gene inactivity |
| how do transcription factors work? | most transcription factors will be made by hormones
transcription factors and RNA polymerase bind to DNA forming a transcription initiation complex
the transcription initiation complex attaches to the promoter region
transcription can happen now |
